Heat Index Calculator
Estimate how hot it feels from air temperature and relative humidity using NOAA heat-index equations.
Hit Calculate to see your heat zone
Calculate to compare air vs feels-like
Metrics appear after calculation
Your explanation appears here
Direct sun, low wind, heavy clothing or hard activity can make the real heat stress higher.
Your plan appears after calculation
Test another temperature or humidity without changing the main result.
Calculate your baseline first
This tool uses the NOAA heat-index approach: the Rothfusz regression for hot, humid conditions and a simpler apparent-temperature fallback when the full regression is not appropriate.
High humidity slows sweat evaporation. Because evaporation is one of the body's main cooling methods, humid air can make the same temperature feel much hotter.
Heat index is normally interpreted for shaded conditions. Direct sun can raise heat stress significantly, so treat outdoor sun exposure as more severe than the calculated number alone.
Results are estimates generated locally in your browser from standard heat-index equations. They are for informational purposes only and are not medical, occupational-safety or emergency advice. Heat illness can occur quickly; follow local weather alerts, workplace rules and professional guidance. VisionVix accepts no liability for decisions based on this output.
